1. Field of the Invention
The present invention relates to an image recording apparatus configured to eject liquid to record an image on a recording medium, and more particularly to an image recording apparatus equipped with an image sensor which picks up a recorded image.
2. Description of the Related Art
Recently, there has been developed an ink-jet printer using a line head having a recording range larger than a width of a recording sheet as a recording medium. In such a line printer, recording for each extremely narrow portion of the recording sheet extending in a direction in which the recording sheet is conveyed is carried out only by a corresponding one of nozzles. Thus, even where there are only a small number of nozzles in which an ink ejection failure occurs such as non-ejection of inks (liquids), variation of an ejected ink amount, and a deviation of a direction in which the inks are ejected, a white patch or line, or unevenness is formed or developed on the recording sheet, thereby deteriorating an image quality by a relatively large degree.
To solve this problem, in an ink-jet recording apparatus disclosed in Patent Document 1 (Japanese Patent Application Publication No. 2006-206742), image sensors of line type operable to read a test pattern recorded on a recording sheet are provided at respective positions each of which is adjacent to and located downstream of a corresponding one of recording heads in a direction in which the recording sheet is conveyed. Any nozzle in which an ink ejection failure occurs is detected on the basis of image data obtained by the image sensors of line type, and a prescribed recovering operation is performed for the nozzle. By a method like this, the nozzle in which the ink ejection failure occurs can be precisely detected to recover such nozzle.
Further, Patent Document 2 (Japanese Patent Application Publication No. 10-95160) discloses a printer in which a line sensor is disposed upstream of the ink-jet heads in a direction in which a recording sheet is conveyed. This printer is configured to detect, by the line sensor, an inclination of the recording sheet relative to the ink-jet heads, and configured to record an image on the recording sheet with no inclination by correcting recording data on the basis of a result of the detection. In accordance with an increase of a conveying speed of the recording sheet in order to meet a demand of high speed recording, there increases a possibility that the recording sheet is conveyed while being shifted and inclined.